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FOR PARTICLES WITH ABSORPTION CROSS SECTION OF 1.E-23 CM**2 NAME EXOTIC IS USED.
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An inclusive γ ray spectrum in p̄p annihilation at rest has been measured with modularized NaI(Tℓ) detectors with statistics several times higher than before. The aim of the experiment was to search for baryonium B in p̄p → γB by detection of narrow lines in the γ ray spectrum. We have not observed any narrow state B with yield greater than 1.5 × 10 −3 per annihilation and with statistical significance higher than 2σ.
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Using the UA2 apparatus, the inclusive cross section has been measured for production of high- p T direct photons in p̄p collisions at s =546 GeV and s =630 GeV . The results are in good agreement with QCD predictions.
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A sample of two-jet events from the UA1 experiment at the CERN $p \bar{p}$ Collider has been used to study the fragmentation of high-energy quark and gluon jets into charged hadrons. Compared with lower-energy jets observed in $e^+ e^−$ and $pp$ collisions, the fragmentation function measured in the present experiment is softer (i.e. peaked to smaller values of z) and the mean internal transverse momentum is larger, mainly because of the effects of the QCD scaling violations. Using our knowledge of the quark and gluon structure functions in the proton, together with the QCD matrix elements, a statistical separation of quark and gluon jets is achieved within the present experiment. The fragmentation function for the gluon jets is found to be softer, and the angular spread of the fragmentation products larger, than is the case for quark jets.
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A study of τ-lepton production in the CMS energy region from 14 to 46.8 GeV at PETRA is reported. The cross section, the decay branching ratio into μν ν , and the electroweak parameters are determined with a total integrated luminosity of 115 pb −1 .
Total cross section calculated from measured channel cross section assuming BR(tau-mu) = 17.6 pct. SIG(Q=MU) is the QED point cross section.
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New data have been obtained on a resonance in the ϕπ 0 system, the C meson, which is formed in the π − p → ϕπ 0 n charge-exchange reaction. The experiment has been performed at the Serpukhov 70 GeV accelerator. The mass and the width of the resonance are measured to be M =1480±40 MeV , Γ =130±60 MeV . The production cross section is determined at a π − momentum of 32.5 GeV / c : σ ( π − p → Cn )· BR ( C → ϕπ 0 )=40±15 nb . The C(1480) meson has an isospin I =1 and spin-parity J PC =1 − − . It is strongly coupled to the ϕπ 0 channel and is considered as a possible exotic meson.
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THE ACCEPTANCE CORRECTED DISTRIBUTION.
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MODEL DEPENDENT ESTIMATION.
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High-statistics data on the reaction π−p→ηπ+π−n at 8.06 GeV/c were obtained. An isobarmodel partial-wave analysis was performed for the ηππ system. The η(1275) meson was confirmed as a narrow IJPC=00−+ resonance. It decays through both δπ and εη. A narrow state with IJPC=00−+ was found in an ηππ decay channel at 1.42 GeV. It has a prominent peak in a δπ decay mode. No significant E(1420) signal with IJPC=01++ was found near the mass region of 1.42 GeV.
No description provided.